Myeloid Cell Leukemia 1 (Mcl-1) is an important anti-apoptotic member of the BCL-2 family of proteins and a master regulator of cell survival. Amplification of the MCL1 gene and/or overexpression of the Mcl-1 protein has been observed in multiple cancer types and is commonly implicated in tumor development. In fact, MCL1 is one of the most frequently amplified genes in human cancer. In many malignancies, Mcl-1 is a critical survival factor and it has been shown to mediate drug resistance to a variety of anti-cancer agents.
Mcl-1 promotes cell survival by binding to pro-apoptotic proteins like Bim, Noxa, Bak, and Bax and neutralizing their death-inducing activities. Inhibition of Mcl-1 thereby releases these pro-apoptotic proteins, often leading to the induction of apoptosis in tumor cells dependent on Mcl-1 for survival. Therapeutically targeting Mcl-1 alone or in combination with other therapies, therefore, is a promising strategy to treat a multitude of malignancies and to overcome drug resistance in many human cancers.